Axonyx Reports Data on Stabilized Brain Volumes in Alzheimer's Disease Patients Treated with Phenserine; Analysis of Brain Scans Suggests Protection against Brain Atrophy.

NEW YORK -- Axonyx Inc. (NASDAQ: AXYX) today reported an analysis of results suggesting stabilization of total brain volume and brain parenchymal fraction of mild-to-moderate Alzheimer's disease (AD) patients treated with Phenserine 10mg or 15mg twice daily (BID) for 26-weeks. The data will be presented in their entirety as a poster in Geneva on Thursday, April 20, 2006 at the 9th International Geneva/Springfield Symposium on Advances in Alzheimer Therapy.

A sub-study, using Magnetic Resonance Imaging (MRI), examined the effects of Phenserine treatment on the brains of 16 AD patients (Phenserine 15mg BID, 8 patients; Phenserine 10mg BID, 7 patients; and placebo, 1 patient). The primary aim of this sub-study was to investigate the potential effect of Phenserine treatment on the volume of different anatomical regions of the brain (brain parenchymal fraction, whole brain and the hippocampus). These patients were part of an earlier reported Phase III, 26-week, double blind, placebo-controlled clinical trial that recruited 377 patients. This sub-study was recently completed to provide further data to potential licensing partners for Phenserine.

Following Phenserine treatment, patients' mean total brain volume and parenchymal fraction remained stable from baseline but decreased in the one placebo patient. Mean changes in brain volume were +0.99% (Phenserine 15mg BID), +2.68% (Phenserine 10mg BID) and -5.15% (placebo) and mean parenchymal fraction changed from baseline by +0.21%, +0.46% and -2.97% respectively. Although not statistically significant, the mean percentage changes of brain volumes seen in the treated groups suggests a preservation of volume compared with the brain atrophy (loss of brain volume) seen in the placebo patient. There was no notable effect in the hippocampal area of the brain; however this may have been due to the difficulty associated with measurements of this small brain structure.

It is well known that Alzheimer's disease is associated with an acceleration of brain atrophy that is generally greater than expected for non-demented persons of similar age. Brain atrophy as measured by MRI has emerged as a potential outcome measure of AD treatments and marker of disease severity and progression. The possible neuro-protection seen in this sub-study may potentially reflect the effects of Phenserine on amyloid beta (A beta) - a protein thought to be a potential cause of Alzheimer's disease and its progression. Phenserine's effects are associated with reductions of A beta levels in pre-clinical studies, as well as a correlation seen between Phenserine levels and a reduction of plasma A beta in Phenserine-treated human volunteers. While the signal from this sub-study of a potential effect of Phenserine on the brains of AD patients is encouraging, the Company notes that MRI brain studies are generally of longer duration and include more patients, particularly in the placebo group. Nevertheless, the absence of brain atrophy in Phenserine treated AD patients in this sub-study is contrary to what would be expected to occur and may justify a definitive MRI evaluation of the effects of Phenserine on brain atrophy in patients with Alzheimer's disease.

About Phenserine

Phenserine is a highly selective inhibitor of acetylcholinesterase (AchE-I), an enzyme that breaks down the neurotransmitter acetylcholine, a neurotransmitter important to memory and cognitive function. Unlike other AchE-I's, which only suppress the activity of the enzyme, Phenserine has been shown to have two mechanisms of action: (1) the inhibition of the AChE enzyme, and (2) inhibition of the synthesis of A beta - a protein thought to be a potential cause of Alzheimer's disease and its progression.

About Axonyx

Axonyx Inc. is a U.S.-based biopharmaceutical company engaged in the acquisition and development of proprietary pharmaceutical compounds for the treatment of Central Nervous System disorders. The Company currently has three compounds in development for Alzheimer's disease; Phenserine - a potential symptomatic and disease progression treatment of mild to moderate Alzheimer's Disease (AD); Posiphen(TM) - a potential disease progression treatment for AD now in Phase I; and BisNorCymcerine (BNC) - a potential symptomatic treatment of severe AD in the pre-Investigational New Drug (IND) stage.

This press release may contain forward-looking statements or predictions. These statements represent our judgment to date, and are subject to risks and uncertainties that could materially affect the Company, including those risks and uncertainties described in the documents Axonyx files from time to time with the SEC, specifically Axonyx's annual report on Form 10-K. Specifically, with respect to our drug candidates Phenserine, Posiphen(TM) and BisNorCymserine, Axonyx cannot assure that: any preclinical studies or clinical trials, whether ongoing or conducted in the future, will prove successful, and if successful, that the results can be replicated; safety and efficacy profiles of any of its drug candidates will be established, or if established, will remain the same, be better or worse in future clinical trials, if any; pre-clinical results related to cognition and the regulation of beta-APP and/or amyloid beta will be substantiated by ongoing or future clinical trials, if any, or that any of its drug candidates will be able to improve the signs or symptoms of their respective clinical indication or slow the progression of Alzheimer's disease; any of its drug candidates will support an NDA filing, will be approved by the FDA or its equivalent, or if approved, will prove competitive in the market; Axonyx will be able to successfully out-license any of its drug candidates; Axonyx will be able to successfully in-license any additional compounds; or that Axonyx will have or obtain the necessary financing to support its drug development programs. Axonyx cannot assure that it will be successful with regard to identifying a (sub-) licensing partner for any of its compounds. Axonyx undertakes no obligation to publicly release the result of any revisions to such forward-looking statements that may be made to reflect events or circumstances after the date hereof or to reflect the occurrence of unanticipated events.